1. Field of the Invention
The present invention relates generally to a die cutting press and, more particularly, to a registration system for registering defined areas of web, strip or sheet material with a die unit provided on the cutting press in order to permit accurate cutting of the material.
2. Discussion of the Prior Art
A die cutting press is disclosed in U.S. Pat. No. 4,555,968, to Raney. The press disclosed in U.S. Pat. No. 4,555,968 has a shiftable die unit supported on a cushion of air, and the die unit is movable laterally of the direction of travel of the web or strip as well as rotatably about an upright axis perpendicular to the material in order to bring the die unit into precise registration with defined areas of the material to be processed or cut by the press.
Automatic operation of this known press is provided by a control system having two groups of photo-optical sensors which are disposed to detect the presence of two T-shaped marks provided on opposite sides of the material adjacent each defined area to be cut. The control system is electrically coupled to servomotor mechanisms for adjustably positioning the die unit once advancement of the material is interrupted and a defined area on the material is in general proximity to work structure of the press die unit.
Although a die cutting press having an automatic die registration system, as illustrated in U.S. Pat. No. 4,555,968, represents a significant advance in the art, it would be desirable to increase the operational speed of such a press so that greater amounts of material can be processed. However, it is important that extreme registration accuracy of the die unit with the defined areas be maintained so that the defined areas are precisely severed from the material within very small dimensional tolerances.
As shown in U.S. Pat. No. 4,697,485, to Raney, a die cutting press is provided with a registration system which is operable to provide precise alignment of a shiftable die cutting unit along two axes during the time that the material is advanced along a third axis toward the die unit, so that as soon as a defined area of the material reaches the die unit, the press can be immediately actuated to subject the material to the die cutting operation. Continuous monitoring of an elongated indicator strip provided on the material enables the die unit to be shifted as necessary during travel to insure lateral and angular registration prior to the time that material advancement is interrupted.
The registration system as illustrated in U.S. Pat. No. 4,697,485 represents another significant advance in the art. However, it would be desirable to further increase the operational speed of such a press so that greater amounts of material can be processed. It is also desirable to increase the accuracy of the positioning operations carried out by the system in order to reduce registration errors that may result in a defective product.